不同应变率下纳米多晶Cu/Ni薄膜变形行为的分子动力学模拟

Molecular Dynamics Simulations of Deformation Behaviors for Nanocrystalline Cu/Ni Films Under Different Strain Rates

用分子动力学方法模拟了纳米多晶Cu/Ni薄膜在不同应变率下进行应变加载时的变形行为与力学性能。结果表明:Cu/Ni薄膜在较高的应变率加载情况下具有较高的屈服极限和应变率敏感性(m)。应变率为108s-1时Cu/Ni多层膜的界面上产生孔洞,而应变率为1010s-1时纳米多晶Cu薄膜出现碎裂。在较高的应变率加载条件下,Cu,Ni薄膜中FCC,HCP,OTHER原子团分数变化都很显著,而较小应变率时只有Cu薄膜的结构变化明显。模拟结果还表明,应变率增加有利于堆垛层错的形成,但应变率超过某一值时无序原子团增加会阻碍堆垛层错原子团的生长。

Molecular dynamics simulations are carried out to investigate the deformation behaviors and mechanical properties of nanocrystalline Cu/Ni films under conditions of tensile strain at different strain rates. The results indicate that the Cu/Ni films have higher yield strength and higher strain rate sensitivity（re）at the higher strain rate. The nucleation of voids in Cu/Ni multilayers＇ interface is ob- served at a strain rate of 108s-1, whereas spallation in nanocrystalline Cu films is appeared at a strain rate of 1010 s-1. For the higher strain rate loading conditions, the FCC, HCP, and OTHER atomic groups are changed significantly both in Cu and Ni films. However, striking structural changes are found only in the Cu films under conditions of tensile strain at lower strain rate. The simulation re- sults show that increasing strain rates are benefit to the formation of HCP structure, while if the strain rates exceed a certain value, the increasing disorder atomic groups may impede the growth of HCP atomic groups.